Vehicle brake



Sept. 20, 1960 H. J. BUTLER Re. 24,

VEHICLE BRAKE Driginal Filed Oct. 26. 1955 a Sheets-Sheet 1 E? 20 J7 Z?INVEIVI'OR H. J. BUTLER VEHICLE BRAKE Sept. 20, 1960 3 Sheets-Sheet 2Original Filed Oct. 26. 1953 A ILQ-- Sept. 20, 1960 H. J. BUTLER Re.24,870

VEHICLE BRAKE Original Filed Oct. 26, 1953 v 3 Sheets-Sheet 5 ReissuedSept. 20, 1960 VEHICLE BRAKE Henry James Butler, Sutton Coldfield,England, assignor to Dunlop Rubber Company Limited, London County,England, a British company Original No. 2,754,936, dated July 17, 1956,Ser. No. 388,211, Oct. 26, 1953. Application for reissue May 2, 1958,Ser. No. 733,791

Claims priority, application Great Britain Nov. 11, 1952 12 Claims. (Cl.1887B) This invention relates to disc brakes for vehicles, and

more particularly to disc brakes for motor vehicles and the like.

In our British Patent No. 688,382 a disc brake assembly for motorvehicles and the like is described comprising an annular rotatable brakedisc, a non-rotatable housing straddling a periphery of the disc andcovering a portion only of the braking surfaces thereof and providedwith a pair of coaxial cylinders, one on each side of the disc, eachcylinder being connected to a source of fluid pressure, a plungerfluid-tightly slidable in each cylinder and a pad of friction materialinterposed between each plunger and the adjacent face of the disc,whereby frictional engagement is effected between the disc and pads.when the cylinders are pressurized. The brake is described as having thecylinders formed integrally with the housing and two or more cylindersmay be provided on each side of the disc.

The rapid generation of large quantities of heat which occurs underpresent day conditions, particularly in the braking of aircraft andhigh-powered motor vehicles, tends to cause trouble not only by brakefade, resulting from overheating of the friction pads, but also fromdeterioration of seals and from heating of the hydraulic fluid usuallyemployed for brake operation.

Moreover in disc brake constructions heretofore known the replacement ofworn brake pads is dififcult and cumbersome.

The object of the present invention is to provide a disc brake,preferably for motor vehicles and the like, which is an improvement onknown brakes, particularly in respect of avoidance of the difficultiesreferred to in the preceding paragraph.

According to the invention a disc brake assembly comprises an annularrotatable brake disc, a non-rotatable caliper straddling a periphery ofthe disc and covering a portion only on the braking surfaces thereof, apair of coaxial cylinders one on each side of the disc detachablysecured to said caliper and spaced a short distance therefrom, frictionpads slid-able through holes: in said caliper to frictionally contactsaid disc, means for supplying pressure fiuid to the cylinders and aplunger fluidtightly slidable in each of said cylinders to force saidpads into frictional engagement with said disc.

Preferably the cylinders are formed in a cylinder block, and said blocksare secured to the caliper through spacing members, therebysubstantially isolating the cylinder block from the parts of the brakewhich are liable to heat up during a braking operation. The cylinderblocks can also be easily removed for maintenance purposes or to replacethe friction pads. Preferably also a distance piece which may be made ofan insulating material, is inserted between the plungers and thefriction pads, to reduce still further transmission of heat to theplunger seals and hydraulic liquid. A flexible annular shield ispreferably fitted between the distance piece, or a member associatedtherewith, and the open end of the cylinder to prevent the entry offoreign matter, moisture and the like.

In order that the invention may be more fully described, reference ismade to the accompanying drawings, of which:

Fig. 1 shows a section through a disc brake and wheel assembly for amotor vehicle;

Fig. 2 is a view of the disc brake assembly of Fig. 1, excluding thewheel and looking in the direction of arrow A;

Fig. 3 is a section through BB of Fig. 2;

Fig. 4- is a section through CC of Fig. 2, and

Fig. 5 is a part sectional view through a double-wheel and disc brakeassembly for a heavy vehicle.

In the embodiment of the invention illustrated in Figs. 1 to 4 the brakecomprises an annular disc 1 provided at its inner periphery with adished annular flange 2 which is secured at its inner periphery by nutand bolt assemblies 3 to an annular flange 4 extending outwardly fromthe rotatable hub 5 of a vehicle wheel 6.

An annular flange 7 extends outwardly from a nonrotatable axle casing 8and secured thereto by not and bolt assemblies 9 is a torque plate 10which extends radially to a location adjacent the inner periphery ofsaid disc. A caliper 11 of substantially U-section straddles the outerperiphery of the disc and covers a minor portion of the braking surfacesthereof, said caliper being secured at one of its inner edges to theouter edge of the torque plate by bolts 12. Each limb of the caliper isprovided with a pair of holes extending axially therethrough, said holesbeing axially aligned with the braking surfaces of the disc, and eachhole is axially aligned with a corresponding hole on the other side ofthe disc.

A cylinder block 13 is secured toeach limb of the caliper, on the sidethereof remote from the disc, by bolts 14 (Fig. 3), which extend throughclearance holes in said block and through spacing members 15 and havetheir ends secured to the caliper. A gap is thus provided between theadjacent faces of the block and the; limb of the caliper. A spring 16 isprovided between each spacing member 15 and the adjacent side of theblock to maintain a small clearance therebetween, and thus allow for adifferential in expansion when the parts are heated by operation of thebrake.

Each cylinder block contains two cylinders, the open ends thereof beingpresented towards the limbs of the caliper and each cylinder is axiallyin line with an associated hole through one of said limbs. A plunger 17is provided with a sealing ring 18 and is fluid-tightly slidable in eachcylinder. The inoperative face of the plunger is recessed to accommodateone end of a cylindrical distance piece 19, the other end of which isaccommodated in a recess in a pivoting member 21 the side of whichremote from said recess is provided with a part-spherical projection. Anannular rubber shield 21 has the inner periphery thereof clipped into arecess in the outer periphery of said pivoting member and the outerperiphery thereof clipped into a recess adjacent the open end of theassociated cylinder.

A cylindrical pad of friction material 22 is axially slidable in eachhole in the limbs of the caliper, one end face being adapted tofricitonally engage the adjacent braking face of the disc and the otherend face being centrally recessed to accommodate a boss projectingcentrally from one side of a circular backing plate 23 which abuts saidface and is substantially of the same diameter as said pad. The otherside of the backing plate is provided centrally with a part-sphericalrecess to accommodate the part-spherical projection on the pivotingmember 20. The boss of the backing plate is a tight fit in the recess inthe pad so that movement of the said plate, e.g. away from the disc,will draw the pad out of contact with said disc. A key 24 (Fig. 4) isfitted in a radially-extending groove cut partly in the backing plateand partly in the adjacent face of the pad, and this key prevents thepad from rotating about its own axis.

A space is provided between each plunger and the base of its associatedcylinder. Said spaces of two axiallyaligncd cylinders are connected to asource of pressure fluid through fluid connection 25, and said spaces oftwo adjacent cylinders are interconnected by co'nduits 26 extendingthrough the cylinder block. The spaces of this pair of axially-alignedcylinders are connected to bleedvents 27, whereby the hydraulic systemmay be bled.

The operation of the brake is as follows: Pressurization of the spacebetween each plunger and the base of its cylinder as, for example, byoperation of a master-cylinder or the like, forces said plunger towardsthe disc. The plunger carries with it the distance piece and pivotingmember, and the pivoting member, abutting the backing plate, moves thebacking plate to force the associated friction pad into frictionalengagement with the disc.

An advantage of this form of construction is that the cylinders, theplungers and the hydraulic liquid to operate the brakes are allsubstantially isolated from the heat generated on braking, since an airgap is. provided between the cylinders and the caliper. The distancepieces, too, are interposed between the friction pads and the plungers,and these may be made of a heat-insulating material to reduce furtherthe transmission of heat. The hydraulic liquid and the plunger seals arethus not greatly alfected by the generation of heat on braking.

Another advantage is that the annular rubber shield between the end ofthe cylinder and the pivoting member keeps all foreign matter, moistureand the like from the bore of the cylinder. This keeps the cylinder boreclean, prevents rust and corrosion, and enables the plunger to makefluid-tight contact with the cylinder wall throughout its effectiverange of movement.

A further advantage of this construction is that maintenance of thebrake is facilitated. For example, to renew the pads of frictionmaterial it is only necessary to detach the cylinder blocks, remove theremnants of the old pads from the backing plates, fit fresh pads andthen replace the cylinder blocks. The friction pads of the presentconstruction may be of considerable thickness, thus increasing themileage between pad renewals.

If the friction pads and backing plates should tilt slightly due touneven wear on the braking face, the pivo ted connection between saidplate and the pivoting member will ensure that the full braking forcewill still be applied over the braking face of the pad. Springloadeddevices (not illustrated) may be fitted to retract the backing platesand hence the friction pads away from the disc when the braking pressureis removed, said devices incorporating a slipping friction device tocompensate for wear of the pads.

Alternative means to prevent the cylindrical friction pads from rotatingabout their own axes may comprise a key fitted into an axially extendingslot formed partly in the hole through the caliper and partly throughthe friction pad.

In another embodiment of the invention, illustrated in Fig. 5, a discbrake is provided for a. twin wheel assembly for a heavy commercialvehicle or the like. A sec tional view of the part of the twin-wheel isshown diagrammatically at 30.

An annular disc 31 is secured at its inner periphery to one end of asubstantially cylindrical member 32, the other end of which is securedto, and rotatable by, the vehicle wheel. A caliper 33, of substantiallyU-section straddles the outer periphery of the disc and covers a minorportion only of the braking surfaces thereof and said caliper is securedto a non-rotatable part 33 of the wheel assembly by means of a ringclamp 33* secured to the non-rotatable part 33 by bolts 33. Said calipermay be provided, at the outer periphery thereof, with a plurality ofradially-extending holes 34 which not only lighten the caliper butprovide also for a more efiicient dissipation of heat from the disc.

The two limbs of the caliper are each provided with an arcuate hole 35extending axially therethrough, the hole in one limb being axiallyaligned with the hole in the other limb, and both holes areaxially-aligned with the braking surfaces of the disc. Each of saidholes is provided, on each of the curved opposite sides. thereof, withtwo axially-extending part-cylindrical recesses 36 which extend from theside of the hole remote from the disc to a location about three-quartersof the distance through said limb.

Two arcuate pads of friction material 37 in side-by-side relationshipare slidably fitted through each of said holes, one end face of each padbeing adapted to frictionally engage a braking surface of said disc andthe other end face abutting an arcuate hacking plate 38 which is alsoaxially slidable in said hole. Each backing plate is provided with fourpart-spherical lugs 39 to slidably engage in the part-cylindricalrecesses .36 of the holes 35.

Two cylinder blocks 40 are provided, each having two cylinders formedtherein, and each block is secured through spacing members (notillustrated), as in the previous embodiment of the invention, to a limbof the caliper on the side remote from the disc. A plunger 41 isfluid-tightly slidable in each cylinder and a space between said plungerand the base of the cylinder is connected to a source of fluid pressure.

A distance piece 42 is fitted in each cylinder, one end thereof abuttingthe plunger and the other end abutting one end of the backing plate. Anannular rubber shield 43 has its inner periphery clipped in a groove inthe distance piece and its outer periphery clipped in a gro'ove adjacentthe open end of the cylinder.

Two spring loaded devices 44 are associated with each cylinder, theheads of the pins being secured to the lugs of the backing plate. Thesprings serve to retract the backing plate after operation of the brakeand a slipping friction device allows the plate to move towards the discto compensate for wear of the friction pads.

The operation of this brake is similar to that previously described. Onpressurizing the space between the plunger and the base of each cylinderthe plungers are moved towards the disc and, acting through the distancepieces and backing plate force the friction pads in frictionalengagement against the braking surfaces of the disc. This deceleratesthe disc and hence the wheel. On release of braking pressure the springretraction device retracts the backing plates to allow the pads to moveaway from the disc and if wear of the pads occurs the slipping frictiondevice automatically compensates for said wear.

As the friction pads wear during use the backing plates move closer intowards the disc until the lugs 39 thereon strike the ends of thepart-cylindrical recesses 36. This indicates to the operator that thefriction pads require renewal.

Disc brakes of the type herein described are not limited to vehiclewheels but may be used as transmission brakes for vehicles or machineryand the like.

Having described my invention, what I claim is:

1. A disc brake assembly comprising an annular ro tatable brake disc, anon-rotatable caliper straddling a periphery of the disc and covering aportion only of the path of rotation of the braking surfaces thereof, apair of coaxial cylinders one on each side of the disc detachablysecured to said caliper, friction pads slidable through holes in saidcaliper to frictionally contact said disc, means for supplying pressurefluid to the cylinders, a plunger fluid-tightly slidable in each of saidcylinders to force said pads into frictional engagement with said disc,and spacing members at spaced intervals between said cylinders and saidcaliper to provide an air space therebetween and between each of saidplungers and associated friction pads to provide an air spacetherebetween to prevent the transmission of heat to said cylinders andplungers from said brake disc.

2. A disc brake assembly according to claim 1 Wherein the said spacingmembers are formed of a non-heatconductive material.

3. A disc brake assembly according to claim 2 wherein a spring isinterposed between said cylinders and the adjacent end of theirassociated spacing members to provide a clearance therebetween to allowfor differential expansion of the parts.

4. A disc brake assembly according to claim 3 Wherein each friction padis provided, on the side remote from the disc, with a backing platewhich is also slidable in the hole through the caliper.

5. A disc brake assembly according to claim 4 wherein a pivoting memberis interposed between said backing plate and the associated spacingmember, said pivoting member having a pivotal connection with saidbacking plate.

6. A disc brake assembly according to claim 1 wherein one end of eachcylinder is open and is provided with an annular flexible shield toprevent the entry of dirt, moisture and the like into the cylinder.

7. A disc brake assembly according to claim 1 Wherein means are providedto prevent movement of said backing plate through said hole beyond apredetermined distance.

8. A disc brake assembly according to claim 1 wherein the friction padsare cylindrical and are prevented from rotating about their own axis bya key or like means.

9. A disc brake comprising an annular rotatable brake disc having anannular braking surface on each side; a non-rotatable housing mounted infixed axial position relative to said disc, said housing having a pairof limbs one on each side of said disc and extending over a portion ofthe path of movement of said braking surface and closely spacedtherefrom, said housing having at least one pair of coaxial guide meanswith one means of each pair in each of said limbs, a friction pad foreach guide means of said housing held and guided in its guide means inmovement toward its respective braking surface of said brake disc; apair of coaxial cylinders for each pair of said guide means and alignedtherewith, one cylinder of each pair being detachably mounted on theoutboard side of one of the limbs of said housing; and a piston for eachcylinder slidable axially therein toward and from the braking surface ofsaid disc and having a thrust element on its inboard side to abut itsrespective friction pad substantially centrally thereof and push saidpad to frictional engagement with said disc, said thrust elementincluding means connecting it to said friction element for universallypivoting thrust contact with said friction element whereby said pad isfree to adjust itself to variations in said disc and to the wear of saidpad by tilting on said thrust element as a pivot to permit limitedtilting of said friction pad about the end of said thrust element andwhereby said cylinder and piston may be detached from said housing freefrom its friction pad and displaced to permit withdrawal and replacementof said pad.

10. The brake disc of claim 9 in which said thrust element of saidpiston comprises a stem extending from the piston to said friction padand having a ball and socket abutment with the friction pad.

11. The brake disc of claim 10 in which said stem has a rounded end andsaid friction pad has a rounded recess to receive said rounded end.

12. The brake disc of claim 9 in which the guide means and friction padshave a larger cross-sectional area than that of their respectivepistons.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS 2,304,774 Ash Dec. 15, 1942 2,466,990 Johnson eta1 Apr. 12, 1949 2,531,341 Meador Nov. 21, 1950 2,614,662 Hawley Oct.21, 1952 2,657,772 Chamberlain Nov. 3, 1953 2,682,320 Chamberlain et a1.June 29, 1954 2,790,516 Wright et a1. Apr. 30, 1957

